I bought a Kenmore 583 a couple months back and the darn thing is trying to run over me! I start out with it going slow, and then for no reason it will suddenly speed up for a couple inches (heading straight for my fingers) and then slow back down to normal for a bit. It just keeps this up as I sew. Looks like its headed to the shop. . .

oh really? I always thought they were singers as they use singer needles and parts. lol, shows what I know!
Love the machine, but it does the speeding up thing without me adding pressure on the foot control.